1. Field of the Invention
The present invention relates to the delivery of instant messages over a network.
2. Description of Related Art
Instant messaging is an increasingly popular form of communication, at least in part because of the convenience of instantaneous transmission of messages. However, as that popularity increases—along with the popularity of other forms of digital communication that may share the same communication channels, network congestion increasingly tends to slow the delivery of instant messages or even to prevent delivery altogether, thereby defeating one of the key advantages of instant messaging.
One common method of sending instant messages is through the use of SIP (Session Initiation Protocol) messages at the application layer and UDP (User Datagram Protocol) packets at the transport layer. SIP is described in, for example, IETF RFC-3261 (June 2002). One method used in SIP is the SIP “MESSAGE” method, in which requests of the type “MESSAGE” are used as instant messages to convey message bodies, such as text, between communicants. The MESSAGE method is described in the Internet Draft “Session Initiation Protocol Extension for Instant Messaging” (Sep. 14, 2002), available from the Internet Engineering Task Force (IETF). UDP is described in, for example, RFC 768 “User Datagram Protocol” (Aug. 28, 1980).
Individuals using an instant messaging system are often provided with a “buddy list” feature. The buddy list is a list of other instant messaging users that the individual wishes to keep track of. The individual is provided with information as to whether each user listed on the buddy list is available for messaging.